Thermionic tube amplifier



Oct. ?1. 1930. A. RIO ET AL THERMIONIC TUBE AMPLIFIER Filed Aug. 6 1928 as: .n n w M 0? 1mm w w m w a g l E E Q 4 .1 l... mwrm l mm v .r, w L, a T d m i E 1 .4 E T1 n .w .a H w M a Patented Oct. 21, 1930 ANDBEBIO AND LUCIEN LEVY, OF PARIS, FRANCE THERMI ONIC TUBE AMPLIFIER i Application filedhugxist 6, 1928. Serial No. 297,782

Amplifying device's consisting of thermionic tubes are already well known which are arrangedin the form of a differential bridge or a Wheatstone bridge and of which the two symmetrical branches of the bridge are co1n-- posed either of compensating resistances or compensating sources of current, for example' accumulator batteries arranged in series, the diagonal of the bridge (diagonal which extends from the common point of the batteries) being formed by the grid filament circuit of a thermionic valve, which permits of amplified control of the variations of any suitable resistance included in one of the two symmetrical branches ofthe said'bridge.

j This latter branch'of the bridge may be formed by a resistance offered by the "anode filament circuit of a thermionic valve or a valve having a number of electrodes of which 2 the grid is subjected to variations in potential determinedby the variation ofa resistance which constitutes forexample; i

Resisting 'coil srdmperfect. di-electrics. Selenium cells or photo-electric cells. Ionization'chambers. e 1

The present invention has for its subject improvements applied to the devices above referred to. These improvements do not con of the anode 'cursistin using the variations 3 rent of a triodemounted in the diagonalof the bridge (which variationscanactuate a controlling apparatus), but on the contrary consists in utilizing thevariations of the resistance of the anode filament circuit of this triode which, for this purpose,'is mounted in such a manner that its anode circuit is included ina'branch of a second bridge arranged in cascade with the preceding bridge.

Under these conditions the anode filament 40 circuit of this triode forms one of the branches of the second bridgewhich is also providedwith a triode arranged in the diagonal bra'nchQthe anode circuit ofthis-triode being adaptedto be connected either to a con trolling apparatusio'r arranged in cascade in abranch of-akthird bridge's'iinilar to the second bridge and soon.

' In the accompanying drawing there are V-illustrated solely by way of example differential bridge devices with amplifying triodes, these devices being arranged in accord-. ance with the present invention.

Figure 1' illustrates diagrammatically a in cascade.

'Figure 2 illustrates device with three difl'erentialranged in cascade.

diagrammatically a bridges ar- The device illustrated in Figure 1 has a first difi'erential bridge A, which comprises device Withtwo differential bridges arranged two balanced batteries 1 and 2 of an elec-I tro-motive force respectively Thenegative pole equal to E and of, one ofthese two batteries (the battery 1) is'connected to-a suitable adjustable compensating resistance 3. The positive pole of the battery 2 is connected to the anode of the controlling triode 4 of which the filament is the common heating battery the filaments .The' grid of the differential which the grid filament connected to 5 which supplies of all the triodes of the device.

triode 6, of

circuit forms the diagonalbranch of the bridge, is connected to the equi-potential point X formed by. the

common point of the two batteries 1 and 2. The filament of thetriode 6 supplied bythe j battery 5, is connected to the resistance 3 and the filament of the controlling triode 4t.

' The differential triodeof the bridge A also forms abranch of the succeeding difi'erential bridge B, the resistance of the anode filament circuit ofthistriode being-arranged incas- 'cade in the branch of the bridge in question which is indicated by the chain dotted lines -II' and 11-11. This second differential bridge is formed by the batteries 1' and 2 connected to the equi-potential'point X, and I the compensating resistance 3 which balances the resistance oi theanodefilamentcircuit of the differential triode'6 triode :6 forms the diagonal bridge.

grid filament circuit of theof the first bridge A. I

difl'erential of this. new

- In the example illustrated in Figure l, the

grid of the controlling triode. 4 variations of potential control-at the points wand 0 aft tion. 1 This device may serve,

and as indicated by broken lines,

receives the which it is desired to er amplifica for example foramplifyv ing modulated currents at an audible frequency, which currents act upon the grid of the controlling triode through the medium of an input transformer 7. Between the points a and a (anode circuit of the difierential triode 6) are included the loud speaker 8 and the anode battery 9.

The compensating resistances and 3 are brought to such a value that the equilibrium of each bridge is obtained in accordance with the equation it V n in which equation n indicates either the resistance of the anode filament circuit of the controlling triode at, or the resistance of the anode filament circuit of the difierential triode 6 which is due to the control triode opposite the point B (for this determined heating of their filaments and a detern ined potential of their grids, this potential may be zero).

In the diagram illustrated in a igure 2 there is illustrated a device provided with a supple-- mentary bridge C identical with the intermediate differential bridge and indicated (in the diagram) between the chain dotted lines IIII and IIIIII. This third bridge is formed by batteries 1" and 2 connected at the equi-potential point X and of the compensating resistance 3", which balances the resistance of the anode filament circuit of the difierential triode 6 of the preceding bridge B. c

The difi' erential triode 6 is arranged in a similar manner to the diiierential triode 6 in the preceding example. The anode filament circuit of the differential triode 6 could also form a branch of a further differential bridge arrangedin cascade at the points a, b, 0 at the outlet from the bridge 0 and so on.

The diagrams illustrated in the accom panying drawings are given (as regards the number of bridges arranged in cascade and the application of the device) only by way of example and not in a limiting sense, the device being adapted to be provided with any suitable number of bridges arranged in cascade and be used for various applications Without departing from the scope of the invention.

1. A thermionic tube amplifying device comprising in combination two batteries in series forming two symmetrical branches of a Wheatstone bridge, a thermionic tube having a plurality of electrodes, the anode filament circuit of said tube forming a third branch of the said bridge, an adjustable compensating resistance forming a fourth branch of said bridge, a second thermionic tube having a plurality of electrodes, the grid filament circuit of said second tube forming the diagonal of said bridge and being located between the common point of the two batteries and the common point of the other two branches of said bridge, and means for varying the potential of the grid of the first mentioned tube, the anode of the first mentioned tube being connected to the positive pole of one of the batteries, the anode filament circuit of the sec ond mentioned tube forming one of the branches or a second. bridge otherwise constituted in the same manner as the first men tioned bridge.

2. A thermionic tube amplifying device comprising in combination two batteries in series forming two symmetrical branches of a l Vheatstone bridge, a thermionic tube having a plurality of electrodes, the anode fila ment circuit of said tube forming a third branch of the said bridge, an adjustable compensating resistance forming fourth branch of said bridge, a second thermionic tube having a plurality of electrodes, the grid filament circuit of said second tube forming the diagonal of said bridge and being located between the common point of the two batteries and the common point of the other two branches of said bridge, and means for varying the potential of the grid of the first mentioned tube, the anode of the first mentioned tube being connected to the positive pole of one of the batteries, the anode filament circuit of the second mentioned tube forming one o1 the branches of a second bridge otherwise constituted in the same manner as the first mentioned bridge, and a third bridge arranged in cascade with the second mentioned bridge, the third mentioned thermionic tube forming a branch of the third mentioned bridge.

3. An amplifying device comprising a plurality of lVheatstone bridges arranged in cascade. the first of said bridges consisting of two batteries arranged in series and forming two symmetrical branches thereof, a thermionic tube having an anode filament circuit forming the third branch of said bridge, a compensating adjustable resistance forming the fourth branch of said bridge and a second thermionic tube having a grid filament circuit forming the diagonal of said bridge which is located between the common point of said batteries and the common point of the said third and fourth branches, said second mentioned thermionic tube having an anode filament circuit forming a branch of the second bridge, said second bridge including two batteries each of which forms a branch of said second bridge, an adjustable compensating resistance forming the fourth branch of said second bridge, and a third thermionic tube forming the diagonal of said second bridge and being located between the common point between the two branches and the common point of the anode filament circuit of the second mentioned tube and of the second mentioned resistance, and means for varying I the potential of the grid of the first mentioned ing bridge,

thermionic tube.

4. An amplifying device comprising a'plurality of Wheatstone bridges arranged in cascade, the first of said bridges comprising two batteries each of which forms a branch of said bridge, a thermionic tube having an anode filament circuit and a grid filament circuit, the anode filament circuit forming a third branch of said former included in said grid filament circuit,

an adjustable compensating resistance formv ing the fourth branch of said bridge, a second thermionic tube having an anode filament circuit and a grid filament circuit, the grid filament circuit nal of said bridge and being located between the common point between the branches formed bv the two batteries and the common 1 formed between the anode filament cir point cuit of the first mentioned thermionic tube and the compensating resistance, each of the remaining bridges consisting of two batteries each of which forms a branch thereof, an adjustable compensating resistance forming a third branch, thefourth branch being formed by the anode filament circuit of the thermionic tube of which the circuit constitutes the diagonal of the precedand a thermionic tube having an anode filament circuit and a grid filament circuit, the grid filament circuit forming the diagonal of said bridge, said diagonal extending between the common point of the branches formed by the two batteries and the common point of the branches formedby the last mentioned resistance and the anode filanient circuit of the thermionic tube'of which the grid filament circuit forms the diagonal of the preceding bridge, and a heating battery common to all the filaments of the thermionic tubes in the various bridges.

ANDRE 1110. LUCIEN LEVY.

bridge, an input transconstituting the diagov grid filament 

